This invention relates to an ATM (Asynchronous Transfer Mode) name system which is for use in a television conference system which carries out a conference between a plurality of conference room terminals through an ATM (Asynchronous Transfer Mode) network. Herein, it is to be noted that each of the conference room terminals is placed in a meeting or conference room and has a function of carrying out a conference by the use of a television set with other conference room terminal or terminals through an ATM network.
Herein, an ATM name system (will be often abbreviated to ANS hereinafter) has been defined in the ATM Name System Specification Version 1.0 (af-saa-0069.000), published by the ATM Forum Technical Committee (November, 1996). The specification has been prescribed on the basis of the DNS (Domain Name Server) determined by IETF (Internet Engineering Task Force) on the requests for comments (RFC) 1034 and 1035.
This shows that the ATM name system (ANS) is similar to the DNS and, therefore, a host name should include a domain name of a hierarchical structure. The ANS finally resolves an ATM end system address (AESA) by executing retrieval by the host name. More specifically, the exemplification has been made as the host name “salmon.data.example.com” in the above-mentioned specification (af-saa-0069.000). In this event, the host name “salmon.data.example.com” is used as a key on retrieval and such retrieval finally resolves or gives an AESA, such as 39.246f.000e7c9c031200010001.000012345678.00.
However, consideration is not made at all in the above-mentioned ANS about application to a television conference that is executed or held by using the ANS. In this connection, the above-mentioned ANS is not suitable for the television conference and has various defects and disadvantages that will be enumerated below.
For example, the ANS in question can not directly resolve an AESA on the basis of a destination conference room terminal because the host name of the hiearchical structure should be used as a key on resolving an AESA. More specifically, resolving an AESA in relation to the above-mentioned host name of “.data.example.com” is carried out by an ANS placed in “.data.example.com” domain.
However, it should be considered that a host name in a domain of “.example.com” without “.data” is resolved in such an ATM network system. In this case, any query should be issued once to an ANS placed the domain of “.example.com” on an upper layer, so as to be informed of an additional ANS placed on a layer equivalent to the layer of “.data”. Thus, the host name is resolved into an AESA by the additional ANS.
Likewise, when a host name “.com” without “.example” is given, a query is issued to an ANS placed on an upper layer of “.com” to have the upper layer ANS introduce an additional ANS placed on a layer equivalent to the layer of “.example”. Finally, the host name is resolved in such an additional ANS. Furthermore, if a host name without “.com” is given, a query is issued to an ANS placed on an uppermost layer to get an ANS on the uppermost layer. As a result, resolution is made by the ANS on the uppermost layer.
From this fact, it is readily understood that the domains should have a hiearchical structure and ANS should be distributed and arranged on the respective layers. In this event, if host names, such as “conference room 1. head office” and “conference room 2. branch A” are given, which should be represented by host names of hiearchical structures. This shows that ANSs are necessary for both the head office and the branch and hardware becomes large in size with the above structure.
Moreover, the ATM Name System Specification Version 1.0 (af-saa-0069.000) never points out problems that might occur in a multipoint conference. In this connection, no consideration is made at all in the specification about an ANS used in the multipoint conference and about using a multipoint conference unit (MCU).